Tank liner with curved flanges, apparatus and method for making same

ABSTRACT

A process and apparatus for forming a flange on the side of a metal sheet and wherein the position of the flange changes with respect to the center line of the sheet. The process comprises holding the metal sheet substantially stationary on a fixed platform, while pulling a series of roller benders, together with an edge-trimming device, along on an arcuate path adjacent to the sheet being flanged. Special clamp means are used to minimize distortion in sheet position caused by stress on the sheet being processed.

United States Patent 191 Struss 1 1 TANK LINER WITH CURVED FLANGES,

APPARATUS AND METHOD FOR MAKING SAME [75] Inventor:

Leigh A. Struss, Nashua, NH. Assignee: Martin Welding, Inc., Lowell, Mass.

Filed: Feb. 15, 1972 Appl. No.: 226,640

US. Cl 72/214, 72/220, 72/181 Int. Cl B2ld 19/04 Field of Search 72/214, 210, 215,

72/178, 220; 113/116 Y, 120 V; 29/l57.30

[56] References Cited UNITED STATES PATENTS 2,108,271 2/1938 Samuel 72/215 Oct. 16, 1973 2,091,474 3/1937 E1110 72/214 X 3,535,905 10/1970 Frizell 72/220 Primary Examiner-Milton S. Mehr Attorney-Pearson & Pearson [57] ABSTRACT A process and apparatus for forming a flange on the side of a metal sheet and wherein the position of the flange changes with respect to the center line of the sheet. The process comprises holding the metal sheet substantially stationary on a fixed platform, while pulling a series of roller benders, together with an edgetrimming device, along on an arcuate path adjacent to the sheet being flanged. Special clamp means are used to minimize distortion in sheet position caused by stress on the sheet being processed.

10 Claims, 9 Drawing Figures PMENIEB UCI I 6 I975 SHEET 1 or a PATENIEB UB1 1 6 I973 sum 2 or 3 PAIENIEI] 0m 1 6 1973 saw 3 or s' TANK LINER WITH CURVED FLANGES, APPARATUS AND METHOD FOR MAKING SAME BACKGROUND OF THE INVENTION It has long been a problem to form sizeable flanges on elongate metallic sheets. This has been especially so when the flange followed an especially complex or compound curve type of path. Usually such flanges have been shaped by manual operations while they are held in a metal brake, an exceedingly expensive practice.

In US Pat. No. 3,462,989, Fischer disclosed an apparatus for flanging sheet material, but Fischer was directing his efforts to forming simple flanges and does not attempt to solve the primary problem faced by applicants, i.e., that of forming a flange with a base line which defines a compound curve on the sheet. Another drawback to the apparatus defined by Fischer was the fact that a large amount of floor space is required for the operation of his apparatus.

Nowhere in the prior art has there been any suggestion of apparatus adapted to form complex flange configurations. Yet such apparatus would have a high utility, especially if it minimized the amount of residual strain left in the metal being worked, thereby providing not only an improved process but more reliable products adopted for utility in constructing such structrues as, say, cryogenic tanks and the like.

SUMMARY OF THE INVENTION Therefore it is a principal object of the invention to provide an improved process and improved apparatus for forming flanged edges on metal sheet material, especially for forming sheets having compound curves along the flange line.

It is a particular object of the invention to provide apparatus for flanging the edges of sheet material which apparatus permits the operation to be carried out in minimal floor space.

A further object of the invention is to provide a means for forming flanges along sheets of varying width, and especially whereon the flanged area must curve with respect to the center line of an elongate sheet being processed.

Another object of the invention is to provide flanging apparatus such as described above which imparts a minimal amount of stress to the metal being worked, thereby making it dependable for use in construction of structures requiring very high structural reliability and integrity.

Another object of the invention is to provide relatively simple apparatus for making complex flanges on elongate sheet.

Still another object of the invention is to provide flanging apparatus which incorporates an integral and improved means for accurately trimming the edge of the material being flanged.

A further object of the invention is to provide apparatus of the type described in the foregoing object whereby the sheet to be flanged is held in adaptive clamp means to minimize the effect of stresses exerted on the sheet during the flanging operation.

Other objects of the invention will be obvious to those skilled in the art on reading the instant invention.

In the practice of the invention, a thin elongate sheet is held on a stationary platform while a travelling rollerbender assembly, together with an edge trimmer, traverse one long edge of the sheet, each sequential rollerbending device in the assembly causing the edge of the sheet to be bent into a more upright position. Sheets to be so processed will usually be trimmed roughly beforehand; however, fine trimming is advantageously accomplished by use of an edge-trimming device mounted for movement with the roller-benders along the stationary platform.

The sheet is firmly clamped to the platform by means of convenient fastening devices at one end; at the other end, however, it has been found desirable to provide a pivoted pressure-clamp means. Most advantageously this clamp comprises a number of pivot points so that it may be self-adjusting to various stress vectors exerted thereon during the processing operation, and thereby insure that such stresses will not cause any undesirable warping of the sheet on the platform. lt has been found that such bending stresses are minimized and most easily accommodated, when this clamp is used while a single side of the sheet is being flanged at a given time.

The platform has two tracks mounted along the sides thereof along which the roller-bender assembly with its rolling and trimming devices are carried during the processing operation. These tracks comprise arcuate sections positioned wherever necessary to achieve the appropriate curve for the flange. Most advantageously the curved sections are placed proximate to the fixed'end of the sheet. In the typical case, this will be convenient because the curves desired in the sheet will be at one end, corresponding to a position in a structure, such as a cryogenic tank, where there is a change in diameter or radii at one end thereof, e.g., where the bottom of the tank curves inwardly to a disked-shaped bottom or top.

In general, the apparatus and process of the invention have been found to be entirely satisfactory for processing stationary elongate sheets while accommodating the strains and stresses encountered in the operation and minimizing the factory floor space required for the operation.

A typical sheet to be flanged in accordance with the invention will be a 304-type stainless steel sheet having an average thickness of about 0.02 inches. Such a material is elected primarily for its utility in making cryogenic tanks, i.e., for its ductility tensile strength, and corrosion resistance. However, as will be obvious to those skilled in the art, the process of the invention can be adapted for processing a wide range of metallic sheet materials. In making cylindrical tanks, it is common that the sheet be somewhat rounded rather than absolutely flat. The sheets processed by the apparatus are often arcuate in shape, say from 3 to 6 in magnitude of are when received in section normal to the long dimension thereof.

ILLUSTRATIVE EMBODIMENT OF THE INVENTlON In this application and accompanying drawings are shown and described a preferred embodiment of the invention. Various alternatives and modifications thereof are suggested, but it is to be understood that these are not intended to be exhaustive and that other changes and modifications can be made within the scope of the invention. The suggestions herein are selected and included for purposes of illustration in order that others skilled in the art will more fully understand the invention and the principles thereof and will be able to modify it and embody it in a variety of forms, each as may be best suited in the condition of a particular case.

IN THE DRAWINGS FIG. 1 is a plan view of the apparatus of the invention, showing two tracks mounted along the sheetholding platform and a pivoted clamping device at one end thereof.

FIG. 1A shows one sheet clamp means.

FIG. 2 shows, in elevation, a roller-bender assembly mounted on a track adjacent to the platform.

FIG. 3 shows, in perspective, a sequential rolling operation.

FIG. 4 is an elevation of a sheet trimmer used in the process of the invention.

FIG. 5 illustrates means for moving rails in relation to the platform, the roller-benders and the sheet being bent.

FIG. 6 is a perspective view illustrating utility of sheets formed according to the invention in the construction of cryogenic tanks.

FIG. 7 shows means for holding a sheet being processed.

FIG. 8 shows a perspective view of a flanged sheet formed according to the invention.

Referring to FIG. 1, it is seen that a sheet-processing assembly comprises a sheet platform 17, two carrier rails 19 mounted adjacent each side of platform 17, and clamp means 29 and 23 mounted at each end of platform 17. At one end of each rail 19 is an arcuate rail section 25. The sheet to be processed on assembly 15 is not shown in FIG. 1. As seen in FIG. 1, rails 19 extend beyond platform 17 at both ends thereof to accommodate the required travel of processing equipment, described below, which is carried on the rail 19.

Clamp means 23, mounted adjacent arcuate rail sections 25 is illustrated in FIG. 1A. It comprises upper and lower clamp bars 27 and 29. These clamp bars are tightened about a metal sheet 31 by bolt-tightening means 33.

The processing apparatus carried on the rails 19, and best seen in FIGS. 2 through 4, include roller'bending modules 35 and edge trimmer 37. Roller bending modules 35, as illustrated in FIG. 2, include a lower roller member 39 comprising a cylindrical section 41 and a truncated conical section 43. The circumference of the cylindrical section 41 is tangentially positioned with respect to a sheet 31 being held on platform 17. The sheet 31 is bent upwardly by being forced against conical section 43, and the angle with which section 43 is positioned with respect to the circumference of section 41 is a measure of the amount of bend applied to the sheet by the module 35 to form a flange 38. Bending pressure is applied by engagement of lower member 39 with an upper cylinder 45 mounted to engage cylindrical section 41 as the assembly is pulled along rail 19. The clearance between rolls 45 and 41 is preferably equal to the thickness of the sheet.

As seen in FIG. 1, a plurality of roller-bending modules 35 are mounted on a rail 19 and pulled along at, say, feet per minute by a winch 47 mounted on extension 48 of a rail 19. Each sequential roller-bending module 35 imparts a somewhat more severe bend to the edge of the sheet being formed. While three modules 35 are shown, preferably six are used in practice.

FIG. 4 also shows a metal trimming device 37 advantageously mounted between two roller-bending modules 35. Although the sheet is rough-trimmed before being placed into the apparatus, it has been found to be more desirable to have the finish trimming done between two roller-bending modules. There are a number of advantages to this feature in that the excess metal to be trimmed is present and can be engaged by the first module 35 to help in performing the bending action, but is trimmed off before it gets to a following module where it could interfere with a proper bending to the increased angular displacement.

FIG. 4 shows details of the trimmer assembly 37. The device comprises two shafts 53 journalled in bearings 55 for rotation. Each shaft 53 carries a roller 57. Rollers 57 are spaced with a roll cutter member 59 on the other shaft to admit, snugly fitted, the edge of metal sheet 31. The frictional engagement of the sheet between rollers 57 and adjacent roll cutter 59 causes the rotation of shafts 53 and of roll cutters 59 carried thereon. Opposing roll cutters are spaced to assure cutting action. The trimmer 37 is mounted in a housing 61 riding on track 19 and is interconnected with brackets (such as those shown at 63) to modules 35 and, consequently, integrated into a roller-bender assembly which is pulled along the length of the track on modulesupporting rollers by the action of winch 47.

In FIG. 1, it will be observed that there are a number of rows of receptors 67 spaced therealong. These are to receive hold-down clamps 69 which may be used for holding down that side of the sheet 31 which is not being processed. Use of such clamps are especially useful when sheets 31 vary markedly in width. Such a clamp 69 is seen in FIG. 7 and comprise a pin 71 inserted in receptor 67. Pin 71 restrains sheet 31 laterally while a hold-down dog 73 contacts the upper side of sheet 31 and holds it down against platform 17. Receptors 69 are advantageously connected to the support bracing 74 which supports platform 17.

As seen in FIGS. 2 and 5, minor lateral adjustments in positioning the rails are carried out by adjusting the lateral position of rails 19. These rails are supported on leg support brackets 75 which are slidingly supported on cross beams 83 (See FIG. 1). Positioning assemblers 77 comprise a stop lever 79 and a threaded positioning bolt 81. Assemblies 77 are so placed along rails 19 that the stop lever 79 can be positioned for engagement with the adjacent end of a lateral brace member, e.g., an l-beam 83 mounted on platform support legs 85.

FIG. 6 is a schematic diagram defining the type of tank which is made possible by use of sheets formed according to the invention. It is seen that the tank comprises a large number of flanged metal sheets 31 which form the sidewall 87 of tank 89. These sheets are not only bent radially to form part of the circumference of tank 89, but they are also bent inwardly to form a major part of the transition curve 91 to the bottom ring 93. Plates 31 are welded to this bottom ring.

Ring 93 is, in turn, welded to radially-arranged bottom plates 95 and these are, in turn, connected to a center ring 97.

Flanges 38, formed according to the process of the invention, are so placed that they are bent inwardly. When the interior edges of these flanges are welded together, the walls of adjacent flanges form a suitable expansion joint or diaphragm 101.

A consideration of the tank shown in FIG. 6 shows that a complex 3-dimensional curve is required for the flange 38. Not only must it curve around the major circumference of the tank, but it must curve inwardly at the bottom of the tank and, at the same position, it must conform to the diminishing width of the flat portion of the sheet. That manufacture of such a sheet is possible is, perhaps, within the ken of those skilled in the metal working art. However, applicants efficient method of manufacturing such a sheet while minimizing mechanical working and residual stresses in the metal is believed to be a significant contribution to the art.

FIG. 8 illustrates a sheet 31 formed according to the invention. Top surface 103 forms part of the inner surface of tank 89. Flanges 38 bend upwardly and inwardly according to compound curve 105, along baseline 107 of the flange.

It is to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which might be said to fall therebetween.

What is claimed is 1. Apparatus for forming a flange on an elongate sheet at least part of the baseline of which flange forms a compound curve, said apparatus comprising:

a stationary platform for supporting said sheet,

means for stretching and clamping said sheet on said platform;

track means positioned along the length of said platform forming means to support a plurality of metalprocessing tools for engaging said sheet along one edge thereof, a segment of said track means forming an arc in substantially the plane of said metal sheet mounted on said platform;

a plurality of longitudinally spaced-apart metal processing tools each including opposed pairs of bending rolls moveably mounted on said track and means for progressively moving said processing tools along said track.

2. Apparatus as defined in claim 1 wherein an edge trimmer is positioned in one of said spaces between two said pairs of bending rolls on said track means.

3. Apparatus as defined in claim 1 wherein said processing tools are connected into a signal assembly moveably mounted (In said track.

4. Apparatus as defined in claim 2 wherein said processing tools are connected into a single assembly, or carriage, moveably mounted on said track and comprise at lease three sets of opposed edge flanging rolls, each having a pressure nip adapted to up-bend said flange to a progressively greater angle than the preceding set, until said flange reaches an angle of normal to the body of said sheet.

5. Apparatus as defined in claim 1 comprising clamp means mounted on said platform, along the elongate edge of the sheet remote from that edge engaged by said tools, for holding said sheet against said platform during edge flanging thereof.

6. Apparatus as defined in claim 1 wherein said stretching means is also a clamp means provided with a plurality of pivot points.

7. A process for making a flanged elongate metal sheet wherein the base line of the flange defines a compound curve, comprising the steps of clamping each opposite end of said elongate planar sheet to a stationary platform, to extend flatwise and immovably therealong with at least one longitudinal edge projecting therefrom;

engaging said longitudinal edge of said flat immovable sheet in the nips of a plurality of pairs of bender rolls, each pair having an upper bender roll and a lower anvil roll;

and drawing said bender rolls longitudinally from one end of said sheet to the other along a line curved with respect to the center line of said elongate sheet to sequentially and progressively bend an edge flange out of the plane of said sheet.

8. A process as defined in claim 7 wherein a metal trimmer is placed between two said pairs of bender rollers, removing part of the metal flange formed in a first pair of rollers before said flange is engaged by a second pair of rollers.

9. A process as defined in claim 7 wherein said elongate metal sheet is held under tension by stretching during said drawing of said bender rolls.

10. A process as defined in claim 8 wherein said elongate metal sheet is held under tension by stretching during said drawing of said bender rolls. 

1. Apparatus for forming a flange on an elongate sheet at least part of the baseline of which flange forms a compound curve, said apparatus comprising: a stationary platform for supporting said sheet, means for stretching and clamping said sheet on said platform; track means positioned along the length of said platform forming means to support a plurality of metal-processing tools for engaging said sheet along one edge thereof, a segment of said track means forming an arc in substantially the plane of said metal sheet mounted on said platform; a plurality of longitudinally spaced-apart metal processing tools each including opposed pairs of bending rolls moveably mounted on said tRack and means for progressively moving said processing tools along said track.
 2. Apparatus as defined in claim 1 wherein an edge trimmer is positioned in one of said spaces between two said pairs of bending rolls on said track means.
 3. Apparatus as defined in claim 1 wherein said processing tools are connected into a signal assembly moveably mounted on said track.
 4. Apparatus as defined in claim 2 wherein said processing tools are connected into a single assembly, or carriage, moveably mounted on said track and comprise at lease three sets of opposed edge flanging rolls, each having a pressure nip adapted to up-bend said flange to a progressively greater angle than the preceding set, until said flange reaches an angle of 90* normal to the body of said sheet.
 5. Apparatus as defined in claim 1 comprising clamp means mounted on said platform, along the elongate edge of the sheet remote from that edge engaged by said tools, for holding said sheet against said platform during edge flanging thereof.
 6. Apparatus as defined in claim 1 wherein said stretching means is also a clamp means provided with a plurality of pivot points.
 7. A process for making a flanged elongate metal sheet wherein the base line of the flange defines a compound curve, comprising the steps of clamping each opposite end of said elongate planar sheet to a stationary platform, to extend flatwise and immovably therealong with at least one longitudinal edge projecting therefrom; engaging said longitudinal edge of said flat immovable sheet in the nips of a plurality of pairs of bender rolls, each pair having an upper bender roll and a lower anvil roll; and drawing said bender rolls longitudinally from one end of said sheet to the other along a line curved with respect to the center line of said elongate sheet to sequentially and progressively bend an edge flange out of the plane of said sheet.
 8. A process as defined in claim 7 wherein a metal trimmer is placed between two said pairs of bender rollers, removing part of the metal flange formed in a first pair of rollers before said flange is engaged by a second pair of rollers.
 9. A process as defined in claim 7 wherein said elongate metal sheet is held under tension by stretching during said drawing of said bender rolls.
 10. A process as defined in claim 8 wherein said elongate metal sheet is held under tension by stretching during said drawing of said bender rolls. 